The invention is developed in order to provide additional cleanroom garb for cleanrooms having purity levels meeting federal and industry standards for a class 100 or cleaner cleanroom (Federal Standard 209 C/D). In such environments, particles generated by replenishment of human skin and particles which the cleanroom operator may carry in his hair are significant sources of contamination. For this reason, a cleanroom outfit consists of material which minimizes particle generation. The user generates additional particles which are sources of contamination, both from clothing worn beneath the cleanroom garb and from the user's body. For this reason, the cleanroom garb must also serve to trap such particles while the user is occupying the cleanroom.
The above functions would easily be accomplished with thin polyvinyl chloride sheeting and elastic bands, but for the need of the garment to ventilate human perspiration in order to provide comfort for the user. Certain fabrics, most notably cotton and wool have an ability to ventilate and also to wick moisture from the body. In very hot, dry weather, wool also provides maximum comfort. The same qualities make wool ideal as a woven fabric for cold climatic conditions. Unfortunately, most of these types of natural fibers are prone to particle generation. Other fabrics, most notably polyester, are less prone to particle generation, but are hydrophobic and therefore become uncomfortable in both hot and cold environments.
In cleanroom environments, climatic conditions can be readily controlled. While moisture is often maintained at a fairly high level, temperature can be precisely controlled, so that hydrophobic fabrics, such as polyester, may be comfortably worn as cleanroom garb, particularly when less hydrophobic fabrics are worn over large parts of the body beneath the cleanroom garb. Since the cleanroom garb covers a large proportion of the surface of the body, it is necessary that the fabric provide a fairly high degree of breathability.
One type of fabric which breathes easily and which is fairly comfortable is Teflon (TM for polytetrafluoroethylene or PTFE) coated fibers, such as Teflon coated polyester. Teflon coated fabrics are sold under the trademark Gore-Tex, by W. L. Gore, of Newark, Delaware. This type of fabric has proven to be rather comfortable. PTFE coated fibers are particularly comfortable when worn in combination with non-hydrophobic undergarments, when worn over the head, or when worn loosely. This fabric functions best when the base fiber is non-elastic.
U.S. Pat. No. 4,385,093, to Hubis, describes a method for producing a multi-component, porous PTFE article. Components of PTFE containing a liquid lubricant are placed in intimate contact, dried, and then stretched in one or more directions. The PTFE components may optionally contain a filler. The resultant product has a virtually uninterrupted structure and possesses very high bond strengths.
U.S. Pat. No. 4,194,041, to Gore, et al., is directed to a waterproof article for use in, for example, protective clothing. The article prevents liquid water from penetrating through to undergarments while at the same time permitting moisture vapor such as perspiration to pass out through the article. The article is thus both breathable and waterproof. The article is layered with a microporous hydrophobic outer layer which permits the passage of moisture vapor but resists penetration by liquid water at elevated pressures and a hydrophilic inner layer permitting the transfer of moisture vapor but preventing surface tension lowering agents such as those contained in perspiration and body oils from reaching the hydrophobic layer.
U.S. Pat. Nos. 3,962,153 and 4,187,390, to Gore, relate to a polytetrafluoroethylene polymer in a porous form which has an amorphous content exceeding about 5% and which has a micro-structure characterized by nodes interconnected by fibrils. The material has high porosity and high strength. It can be used to produce all kinds of shaped articles such as films, tubes, rods, and continuous filaments. Laminations can be employed and impregnation and bonding can readily be used to produce a large variety of articles. Compressed articles of very high strength can also be produced from these porous forms.
U.S. Pat. No. 4,025,679, to Denny, shows a fabric woven from oriented polytetrafluoroethylene (PTFE) strands, in which the strands of the weave are interconnected by a multiplicity of fine PTFE fibrils. To produce this fabric, consisting entirely of PTFE, a woven PTFE fabric is heated substantially unrestrained to a temperature above the crystalline melt point of PTFE and stretched. Alternatively, a woven PTFE fabric may be impregnated with other fluorocarbon polymers, heated substantially unrestrained to a temperature above the crystalline melt point of PTFE, and subsequently stretched, thereby generating a multiplicity of fine fibrils interconnecting the weave.
Cleanroom garb is, at best, inconvenient to put on and remove. While people are known to remain in the fab or other cleanroom areas for an entire 12-hour shift, the usual mode is to leave the cleanroom for coffee breaks, toilet, and meal breaks, each of which require a dress down and dress up of cleanroom garments. For this reason, it is desirable that the cleanroom garb be easily adjusted, usually by the mere act of putting the garment on. It is desirable that the easiest and the most natural way of putting the garment on also results in the most proper fit.
In the case of full headgear, the natural tendency is for a person not to place anything around the face. This means that a strap intended as a face mask and bib has a natural tendency of being worn as a chin strap or scarf. It is also quite important that the face mask be as loose fitting as possible and yet provide for sealing the garment around the face.
For this reason, the cleanroom garb is intentionally made to be fairly loose fitting. The loose fit also permits the garment to be worn by different users, with a minimum of different sizes required. Typically, four sizes are sufficient for most articles of cleanroom clothing.
Loose fitting "billowy styles" do not lend themselves to preventing escape of particles from the edges of the cleanroom garb. Our cleanroom design incorporates an air shower, in which air is continuously flowed from ceiling to floor. Therefore, particles coming from a bottom portion of cleanroom garb tend to be quickly removed from the cleanroom environment. On the other hand, top portions of the garb, such as the underhood, should be sealed. For this reason, the underhood is attached by means of a face mask which is adjusted in tension. This permits the fabric to be selected in accordance with the peripheral comfort of the user, while permitting adjustment to be accomplished by manually adjusting the face mask. In the prior art, this has been done by use of snaps or other fasteners.
Sealing of the garment is usually accomplished by adjustments and by elastic material. Elastic fabrics, such as Lycra (.TM.) have proven popular because they are less constraining than elastic bands co-mingled with material. The elastic fabric has a disadvantage in that it does not breathe as readily as non-elastic materials and the close fit afforded by the elastic material tends to be uncomfortable, particularly when combined with the reduced breathability of the material.
We would like to provide an underhood which is comfortable to the wearer and which provides an ample degree of sealing to prevent cleanroom contamination from the head area. It is important that the garment be comfortable and easy to remove and put on.
The fit of a cleanroom garment, such as an underhood, is important but sometimes conflicts with the ease at which can be put on and taken off. If a garment can be put on and removed as readily as, for example, a cowboy hat, the inconvenience to the user is reduced and the user is likely to properly adjust the garment. Furthermore, if the garment is easily adjusted and is comfortable, it is less probable that the garment will be put on "wrong." This is particularly true of headgear, which tends to be most critical and noticeable with respect to comfort and which is most difficult t fit properly.
A face mask is sometimes used in cleanrooms in order to prevent exposure of the cleanroom environment to contamination which would be caused by the user breathing in the cleanroom. It is likely that the face mask will be adjusted frequently, even if not in the immediate area of sensitive processes. When the face mask is adjusted, the underhood should prevent particles from escaping in the cleanroom.
It is also likely that the same cleanroom garment that is used in conjunction with a hood may also be used as an external garment without a hood. In other words, the underhood also must serve as an external head cover. The dual use implies that the garment must provide comfort in both circumstances, and also provide its cleanroom protection in both circumstances. This means that the dual purpose underhood must provide maximum comfort when worn with an external hood and be comfortable and provide sealing when the hood is removed. These two functions may conflict.
It is therefore desired to provide a tighter sealing function for an underhood. It is desired that the underhood be as comfortable as possible, including at the sealing part; and it is further desired that the adjustability of the underhood be as effortless as possible, thereby enabling the user to easily put the garment on properly and to be comfortable with the garment fitted properly. In other words, it is desired to provide an underhood which has improved comfort, sealing, and is easy to put on and which, because it is comfortable and easy to adjust, is more likely to be fitted properly when in use.
Users often have a wide variety of hair styles, ranging from bald to whatever version of a beehive hairstyle current fashion may dictate. While certain hairstyles are unaffected by tight-fitting headdresses, others are very much affected. A tight-fitting headdress may feel uncomfortable to some users. Since a loose fitting headdress would seldom be in the way of the user, it is advantageous that a hair cover be spacious. Also from a comfort standpoint, the head provides a significant portion of human temperature control. Since the hair draws moisture from the scalp, it is important that the maximum amount of breathability be provided through the headdress. Loose fit is comfortable and less likely to generate particles from friction. It is also desired to prevent loose particles from escaping from the headgear, even though loose fit is provided.